Backup? You kidding?
With a single BD-R disc costing as much as a Hollywood-flick-pressed one, not gonna happen. Due to piracy concerns, blu-rays can be recorded, yes, but at prohibitive cost. The studios managed to kill the media, as far as computers go, as a whole.
As for portable HDDs, on the other hand... I just bought an outdated and almost obsolete USB-2.0 one with a 500GB HDD (465GB actual, whatever) for the same or less price than this BD-recorder. And, oh my gosh, lo and behold, it records 9-10 times more, 5x faster. Plus I don´t have to pry my case open to shove it inside, I can plug it on USB (eg, any-freaking-where). Will my buddies own a BD player on their computers, so they can read my backup? Guess what, anything 5 years old won´t.
For entertainment purposes, however, it has its uses. Or, if for any particular reason, your 4-year-old DVD-recorder caved in, or you can´t find a suitable replacement that will plug in your SATA-only motherboard, that drive will do.